1. Field of the Invention
The present invention generally relates to a color filter substrate (CF substrate) and a liquid crystal display panel (LCD panel), in particular, to a color filter substrate and a liquid crystal display panel, which are able to improve the precision of panel assembly and bear the lateral stress.
2. Description of Related Art
With recent advancement in opto-electronic and semiconductor technology, the technology for fabricating flat displays becomes more mature. For display devices, the liquid crystal display device having advantages of higher image quality, optimal space efficiency, low power and non-radiation has become the main stream on the market. Generally speaking, the liquid crystal display device comprises a liquid crystal display panel and a backlight module. More specifically, the liquid crystal display panel is composed of a color filter substrate, an active device array substrate and a liquid crystal layer.
The characteristics of the liquid crystal display device, such as response time, brightness, contrast and viewing angle, are related to the thickness of the liquid crystal layer. Therefore, the thickness of the liquid crystal layer should be controlled precisely according to optical properties of liquid crystals. Generally, spacers are disposed between the color filter substrate and the active device array substrate to form a gap between the two substrates. Spacers can be divided into ball-shape spacers and photo-spacers. Photo-spacers fabricated by photolithography process can maintain the gap more even, and therefore ball-shape spacers are gradually replaced by photo-spacers.
FIG. 1 is a schematic cross-sectional view showing a conventional liquid crystal display panel. The liquid crystal display panel 100 comprises a color filter substrate 110, an active device array substrate 120 and a liquid crystal layer 130. The color filter substrate 110 comprises a substrate 112, a light shielding layer 114, a color filter layer 116 and a common electrode 118. The active device array substrate 120 comprises a substrate 122, a plurality of thin film transistors 124, scan lines and data lines (not shown). Particularly, the liquid crystal display panel 100 utilizes the photo-spacers 140a to maintain the gap d between the color filter substrate 110 and the active device array substrate 120, such that the liquid crystal layer 130 is sandwiched between the color filter substrate 110 and the active device array substrate 120.
To follow the trend of higher finger pressing stress applied to the liquid crystal display panel 100, the number of the photo-spacers 140a per unit area should be increased. When the user wipes the liquid crystal display panel 100, the photo-spacers 140a are displaced by lateral stress, and therefore displacement occurs between the color filter substrate 110 and the active device array substrate 120. And this would result in light leakage or the center of the liquid crystal display panel 100 would become darker.
As shown in FIG. 2, other photo-spacers 140b are provided to resolve the above-mentioned problems. The same reference numbers are used in FIG. 2 to refer to the same or like parts. In the liquid crystal display panel 200, a planarization layer 126 covers the active device array substrate 120, and a contact opening 126a is formed in the planarization layer 126 to make the pixel electrode 128 electrically connect to the thin film transistor 124. Note that the photo-spacer 140b is disposed in the contact opening 126a, and therefore compared to the liquid crystal display 100 shown in FIG. 1, the liquid crystal display panel 200 can bear larger lateral stress.
Because the dimension of the contact openings 126a is smaller, the precision of the liquid crystal display panel 200 assembly would be lower. As a result, when the user wipes the liquid crystal display panel 200, the photo-spacers 140b would still be displaced if the lateral stress is larger. And the problem of displacement between the two substrates, light leakage and so on would still occur.